In a conventional gas compression refrigerating system having the Rankine cycle, a compressor device of the system is also used as an expansion device when heat energy is collected by the Rankine cycle, for example, as disclosed in Japanese Patent No. 2540738.
In the compressor device of this system, gas, such as gas-phase refrigerant is sucked into a working chamber and the gas is compressed in accordance with a decrease of the volume of the working chamber upon receiving an external mechanical energy, so that compressed refrigerant is pumped out from the compressor device. On the other hand, in the expansion device, high pressure gas is introduced into the working chamber to expand the volume of the working chamber by the pressure of the gas, so that the mechanical energy can be obtained. Accordingly, a flow direction of the gas, i.e. the refrigerant, needs to be reversed, when the function of the fluid machine is changed from the compressor device to the expansion device.
According to the prior art system, as disclosed in the above Japanese Patent, however, an inlet and discharge ports for the refrigerant for an operation as the expansion device are provided on the same side of an inlet and discharge ports for the refrigerant for an operation as the compressor device. And therefore, the compressor device can not be used as the expansion device, as a single mechanical device. As a result, either one of the Rankine cycle (gas expanding) operation and the gas compression operation can not be properly carried out.
More in detail, a check valve is generally provided at a discharge port of the compressor device for preventing the working fluid from flowing in the reversed direction from a high pressure chamber (a discharge chamber) to a working chamber, since the working fluid is compressed by decreasing the volume of the working chamber by moving mechanical movable parts, such as pistons, movable scrolls and so on, and the discharge port communicates the high pressure chamber with the working chamber.
On the other hand, the expansion device generates mechanical output by introducing the high pressure working fluid from the high pressure chamber into the working chamber to move the mechanical movable parts. And therefore, the high pressure working fluid can not be simply introduced from the high pressure chamber into the working chamber because of the check valve provided at the discharge port. As above, the compressor device cannot be used as the expansion device by simply changing over the inlet and discharge ports, to achieve the reversed flow of the working fluid.
In view of those problems, the applicant of this invention has proposed in its prior patent application (Japanese Patent Application No. 2003-165112, corresponding to U.S. patent application Ser. No. 10/764,534) a new fluid machine, in which a high pressure and a low pressure chambers as well as a valve mechanism are provided, so that a fluid flow from a working chamber to the low pressure chamber and another (reversed) fluid flow from the high pressure chamber to the working chamber can be realized in the respective operations as the compressor device and the expansion device. It is, however, disadvantageous in that the waste heat can be collected by the fluid machine (by operating it as the expansion device) only when gas compression operation (by operating it as the compressor device) is not necessary. If the compressor device and the expansion device were separately provided, then the fluid machine would become larger in its structure.